This comes from 2012 Census numbers posted at this link. Hence, the H-1B visa program is being used to fill mid-level software jobs, not just jobs with unique skills that cannot be filled by American candidates.
Furthermore, Labor Condition Applications (LCAs) which are required with each H-1B visa are supposed to protect H-1B and American workers. However, I recently looked at the LCAs disclosed online and posted the results at this link. As you can see, very few are denied and many of those that are certified are rife with errors. For example, there were a number of certified applications that did not appear to contain enough information to determine the workplace location, a critical piece of information for evaluating the requests. Then, I noticed that nearly every application that proposed to pay a salary significantly below the prevailing wage was denied. However, many that proposed to pay a salary many multiples the prevailing wage, suggesting bad salary data, were certified. For example, a request to pay a product consultant $11.4 million a year and a staff dentist $15.5 million a year were certified! That's despite the fact that they listed the prevailing wages as $84,344 and $136,864, respectively. It appears that someone is just applying a set of filters to the data and "rubber stamping" everything else. This seems to agree with a 1996 OIG audit which stated that the Department of Labor's role amounted to little more than a "rubber stamping" for LCA program applications (see this link).
For a further response to Murdoch's editorial, see this link.